Electric heating element.



J'. C. C. MACDNUGH.

ELECTRIC HEATING ELEMENT, APPLICATION FILED sBPT,1z,1911.

Patented Apr. 30, 1912.

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J. C. C. MACDONOGH.

BLBCTRIU HEATNG ELEMENT.

APPLIUATIGN FILED SEPT,12, 1011` 1,024,998, Patel'lted Apr. 30, 1912.

2 SHEBTSYSHBET 2.

JOHN CHARLES CAMPBELL MACDONOGH, 0F LDNDON, ENGLAND.

ELECTRIC HEATING ELEMENT.

Specification of Letters Patent.

Patented Apr. 30, 1912. 1

Application wled September 12, 1911. Serial No. 648,986.

To all .whom it may concerny Be it known that I, Jeux CHARLES CAMP- nncn ll'lAcnoNooH, subject of King of Great Britain, residing at London, England, have invented certain new and useful Improvenxents in Electric Heating Elements7 of which` the following is a specification.

This invention relates to electric heating elelnents formed of coiled wire suitably suppoi-,ted` and to apparatus for using such elements.

The object of the present invention is to proyide a form of electrical heating element which shall be readily assembled Withoutwinvolving skilful or expensive opera tionsandlin which the parts may be readily renewed, while at .the same time the heat rfrom the coils or other heatin material will be radiated directly to the o ject to be heated Without requiring to pass through an insulating layer.

cording to the present'invention, the electric heating element consists of heating coils separated by Walls ofinsulating ma terial with raised an overhanging parts which hold thecoils in place and protect- 'themV frein contact with the object to be heated or the casing of the heating element but'laves said coils open to radiate heat directly to the object to be heated. In this way I avoid the necessity of transmitting the lieat `from the coil to the object t-o be .heated through a layer of insulating material.` The shape and arrangement of the insulating means may be varied within very wide -limits and the heater may be arranged to providevarious grades lof heat. The heating elementsherein described are detachable ILVandto'f such anature that no skill is required in inserting them in place or removing them.A

An' important feature of this invention is that the coils are free to radiate heat to both sides. Thus with a division Wall of substantially I cross section the coils are held in place by the flanges both top and bottom, While the said coils are open to radiateheat both top and bottoln. `When applying this heater to a pot or kettle therefore, I am enabled to use a much greater heating'surface. I propose to use this heat ing surface in kettles and pots by inserting the heating element into a side pocket, the top and bottom walls of which are in contact -with the liquid to be heated and form heating surfacesY In this way there is no heat lost from the heating element. In the l a case of an oven, I may arrange the heating element in a hollow shelf, the upper surface forming a hot plate while the lower surface forms a grill and tltie shelves may be arranged movable while he contacts on the shelves Co-aet with bus bars in the frame of the oven.

The invention will be more readily understood from the following forms chosen 'by Way of example and illustrated in the accompanying drawings, in which:

Figure 1, is a section on the line AB of Fig. 2 and Fig. 2, is a plan view of one form of this invention` largeddetail view showing one forni of the Fig. 3. is an enterminal preferably employed. Figs. 4,'a`nd i i 5, are sectional views illustrating other t forms of the invention. Fig. 6, is a plan View of a circular heat element having insulating pieces of the form shown in either Figs. 4 or 5. Fig. 7. is a section and Fig. 8, is a plan view of another formof thisV invention.

Fig. 9, shows an electric heati ing element according tothis invention applied toa kettle. Fig. l0 shows the invention applied to an oven.

According to the forni .of this invention shown in Figs. l and 2, the heating coil'a.,

is continuous and is laid in any suitable i" sinuous form, for exainpl'v in loops with straight parallel legs and is connected at each of its ends to the terminals b and 0. Theseterlninals may be separate as shown or may be arranged closely together so as to fit any standard size of plu.. 'As shown in Fig. 3, the terminals b and c, are preferably composed of two parts p and q. Each end of the coils a, is passed through a sawcut or groove p', on the fpart y g, which is inserted in an opening in `the ck d. The part p, is rovided with a' tapped hole in which tiere screws the A threaded part o', of the externally project-l ing plug y. The wire of the coil a, after passing through the groove p', and a Washer fr, is wound around the threaded partV q', and the externally projecting plug g, is then I tightened'in place. By means of this con# struction the actual terminal of the Wire is accessible from the exterior and eflicient contact is assured by the wire passing through the groove p. The end of 'the wire is also to some extent cooled by its metallic contact with the inner art p. If desired the part p, may be extendjed to form the external plug and in this case an ordina nut would engage with an external thread on the pro'ectin part of the plug.

The terminals an c, are embedded in a block d, of suitable insulating material capable of standing heat. The block d, and projections e, are of the cross section shown in Fig. 1. If desired these projections may be of I shape in cross section. The essential features of the projections e, are that they form an insulating wall with overhanging parts e', which partially embrace coils a, so as to'leave parts of said coils open, the amount of the overhan being less than the half diameter of the coil so that a space is left between the opposite edges of the overhanging parts. The upper surface of the projections e, is above the level of the f element is carried by;

top ofV the coils. The heating element is completed by an insulating block f, having projections g, of similar cross section to the projections e, on the block d. The entire a holding frame which is conveniently in t e form of a metal casing la., which may consist of both an upper and lower plate or may merely be in the form of a binding edge as indicated in the drawing.

It wi l be seen thatby means of the present invention, a simple and effective construction is provided by which it is impossible for the coils to short circuit against the bottom surface of the kettle or other object to be heated or against the walls of the casing of the element. The projections or insulating walls e and g, also erform the function of holding the -coils in place and making the entire element of simple and strong construction. It will be understood that if desired, the pro'ections e and g, forming the insulating wal s between "the coils may be made separate from the blocks d, and f, as hereinafter described und their form and shape maybe varied within wide limits.

Another form of the invention is illustrated in Fi 4, as applied to a circular element in-w ich the sinuous form of the coil is obtained by laying it in volute or substantially concentric circles. In this case the coils a, are inclosed in annuli formed bg the ribs/c, and a base m. On the top of t e ribs there are supported detachable rings xn', which form the raised and overhangi parts pf the insulating walls between t e coils. Instead of providing the base piece m, with ribs as shown in Fig. 4, the'coils may be simply laid concentrically in a plain casing and subsequently separated by means of rings o, having raised and overhanging parts in accordance with this invention.

The ribs lc, and the rings o, are broken at one point of the circumference as shown at Fig. 6, so as to allow of the interconnection of the coils. The coils are in the form shown in Fig. 6, connected in series and two terminals b and c, are provided which project from the bottom of the heat element. If desired, however, the terminals b and c, may be arranged at the side of the element.

Another form of this invention is illustrated in Figs. 7 and 8. In this case the insulating pieces between the coils a, are of I shape in cross section and are in the form of rin s arranged as a volute as shown in lan in ig. 8.` Y he heating elements above describedfare preferably inserted loose] in place at the point required and' no skill is necessary yin detaching or inserting them in place.

IIn the form of this invention illustrated in Figs. 1 and 7, it will be seen that the coils a, are open both top and bottoni-toradiate heat. This enables this form of ter to be used on both sides. rIVhus for toasting or grilling purposesV the elements might be arran in a vertical plane and both sides woul then be eective as heaters. In ket` tles the heati surface of the kettle would be disposed on oth sides of the element and in the case of ovens the heater would be arranged horizontally as a shelf or parallel to the shelves proper so that both the 1 W and lower surfaces of the heater souls 'be The oven may also be provided.

eiective. y with vertical heating elements.

For the purpose of illustrating' typical'` ways in which this invention maybe emp loyed, I have shown the invention applied to a specic form of kettle and also'to an oven.

Referring to Fig. 9, the kettle 11, is provided with heater 13, is'ilisposed. It will be seen here that the heating surfaces 14, 15, are arranged on both sides of the heater so that the maximum heating eifect is produced.' Of course instead of using a side pocket the kettle may be arranged in two parts connected by tubes, the heaterbeing disposeiL between the arts. The essential feature is side pocket 12, in which the that the heating surface isdisposed on both j sides of the element. A clip 16, may be employed for holding the heater in place. The

ettle is preferab made to rest on' a stan 17, to which the clip 16, is attached.

According to the form shown in Fig. 10, the casing of an oven has bus bars, 18, 19 20 fitted externally and these are connect-ed to the source of current with all usual and necessary intermediate switches and the like. The heaters 24, are supported on ledg 25,

fixed to upriglits 21, at the sides of the oven. The terminals of the coils of the heaters engage in sleeves 22, which pass through the oven casing to connect with the bus bars 18, 19, 20, being ably insulated from the casing of the oven. The oven is conveniently lagged with suitof course suittions of the coil and projections from said walls above and below the coil, said walls and projections being dimensioned to emcentric clrcles a divi ing and holding well of insulating material located between adjacent sinuations and. of substantially the same length as the coll, said wall being of substantially I section.

:IWMMB 13. In combination with a, .pocketed heater an electric heating element located in said pocket and comprising sinuous electrie heating coils and ,insulatin walls of substantially I shape in ci'oss section located between and of substantially the same length as adjacent lengths of said coil.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

JOHN CHARLES AMPBELL MACDONOGH.

Witnesses:

H. MATHYS, P. S. H. ALEXANDER. 

